border-1px($color)
  position relative
  &:after
    display block
    position absolute
    left 0
    bottom 0
    width 100%
    border-top 1px solid $color
    content ''
bg-image($url)
  background-image url($url+"@2x.png")
  @media (-webkit-min-device-pixel-ratic:3),(min-device-pixel-ratic:3)
    background-image url($url+"@3x.png")
